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Reentrant Phase Coherence in Superconducting Nanowire Composites

DOI: 10.1021/acsnano.5b05450 DOI Help
PMID: 26727335 PMID Help

Authors: Diane Ansermet (Nanyang Technological University) , Alexander Petrovic (Nanyang Technological University) , Shikun He (Nanyang Technological University) , Dmitri Chernyshov (ESRF) , Moritz Hoesch (Diamond Light Source) , Diala Salloum (Sciences Chimiques, CSM UMR CNRS 6226) , Patrick Gougeon (Sciences Chimiques, CSM UMR CNRS 6226) , Michel Potel (Sciences Chimiques, CSM UMR CNRS 6226) , Lilia Boeri (Institute for Theoretical and Computational Physics, TU Graz) , Ole Krogh Andersen (Max Planck Institute for Solid State Research) , Christos Panagopoulos (Nanyang Technological University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Nano , VOL 10 (1)

State: Published (Approved)
Published: January 2016

Abstract: The short coherence lengths characteristic of low-dimensional superconductors are associated with usefully high critical fields or temperatures. Unfortunately, such materials are often sensitive to disorder and suffer from phase fluctuations in the superconducting order parameter which diverge with temperature T, magnetic field H, or current I. We propose an approach to overcome synthesis and fluctuation problems: building superconductors from inhomogeneous composites of nanofilaments. Macroscopic crystals of quasi-one-dimensional Na2−δMo6Se6 featuring Na vacancy disorder (δ ≈ 0.2) are shown to behave as percolative networks of superconducting nanowires. Long-range order is established via transverse coupling between individual one-dimensional filaments, yet phase coherence remains unstable to fluctuations and localization in the zero (T,H,I) limit. However, a region of reentrant phase coherence develops upon raising (T,H,I). We attribute this phenomenon to an enhancement of the transverse coupling due to electron delocalization. Our observations of reentrant phase coherence coincide with a peak in the Josephson energy EJ at nonzero (T,H,I), which we estimate using a simple analytical model for a disordered anisotropic superconductor. Na2−δMo6Se6 is therefore a blueprint for a future generation of nanofilamentary superconductors with inbuilt resilience to phase fluctuations at elevated (T,H,I).

Journal Keywords: superconductivity; nanofilaments; quasi-one-dimensional; reentrance

Subject Areas: Physics, Materials

Facility: ESRF